Trichomoniasis is a venereal disease caused by the protozoan parasite, Tritrichomonas foetus. The infection is confined to the lower reproductive tract of the female; i.e., the uterus, cervix and vaginal vestibule. In the male, T. foetus is found in the preputial cavity and less commonly in the urethral orifice. Transmission is almost exclusively by coitus.
Trichomoniasis is a worldwide disease of cattle. In infected cows, clinical manifestations of the disease are: early embryonic death, abortion, pyometra, and infertility, all of which result in reduced calf production. Prevalence increases with the age of the bull, possibly due to deepening of crypts in the preputial epithelium. Therefore, older bulls tend to remain long-term carriers. Infection rates are similar in both Bos taurus and Bos indicus cattle Yule et al., Parasitol. Today, 5(12), 373-377 (1989)!. A suggestion that there is a breed difference is susceptibility to T. foetus has not been substantiated.
The prevalence of trichomoniasis in bulls within a herd reported from around the world varies from 5.8-38.5% in California and 26.4% in South Africa, to 30.6-50% in Australia Kimsey et al., J. Am. Vet. Med. Assoc., 177, 616-619 (1980)!. Losses due to reduced milk and calf production in a California dairy were calculated at U.S. $665.00 per infected cow Goodger et al., J. Am. Vet. Med. Assoc., 189, 772-776 (1986)!.
Although trichomoniasis is purely a localized infection, the parasite does come into close contact with epithelial tissue at the site of colonization. The presence of circulating anti-T. foetus antibodies has been established by several assay systems. Naturally infected cattle have low circulating antibody levels. Highest titers have been seen in animals experiencing abortion and pyometra. However, serological tests, including agglutination, complement fixation, and gel precipitation, have failed to detect naturally infected cattle. Adequate antibody levels have been induced in cattle by inoculation of live parasites as well as various killed preparations of T. foetus. Live parasites generally stimulate production of antibody at higher levels than killed preparations. The circulating antibodies, however, reportedly do not come into contact with the parasite and supposedly play no protective role B. M. Honigberg, "Trichomonads of Veterinary Importance, Trichomonads of Importance in Human Medicine", in Parasitic Protozoa, Vol. II, J. P. Kreier, ed. (1978)!.
A number of T. foetus vaccines have been described Yule et al., supra (1989); Clark et al., Aus. Vet. J., 60(6), 178-179 (1983); and Clark et al., Aus. Vet. J., 61(2), 65-66 (1984)!. However, a reliable and highly effective vaccine has not been produced. There is a need for a vaccine preparation that can effectively eliminate T. foetus infection from animals and immunize uninfected animals.